I’m on the BYU cross country, so I have a pretty good idea how much people worked out on their missions. I only know of one person that ran consistently on his mission. One other person ran consistently for the last third of his mission. Other than them, I can’t think of anyone that ran frequently.
During my two year mission, I averaged 0.8 miles a day. I basically ran 3-4 miles once a week for most of my mission, and it was almost always slower than 8:00 pace. I only had one companion that was willing to run with me every morning (my very first companion), and he got mad at me for running ahead and looping back for him. So I had to run slow with him to maintain the peace. Those runs were usually about 2.5 miles and we did that for about two months.
When I didn’t go running, I would have to stay in the apartment with my companion and find some way to work out. Honestly, there were a lot of times where I was too tired to work out so I would do a couple push ups, call it good enough, and move on with the rest of my day.
People don’t really believe that we, missionaries, follow all the super strict rules like always staying with our companion or following the schedule (30 minutes for exercise time), but the very large majority do. I never left my companion to go on a run by myself. That was against the rules, and I wanted to be obedient. Most of the guys on the team were very similar to me. They wanted to run, but their companion didn’t want to.
It took me about 6 months after coming home to return to my peak high school fitness. If you have any more questions, feel free to ask me.